MCExpr: Avoid UB by evaluating this shift as unsigned

We hit undefined behaviour in some MCExpr tests when the LHS of a left
shift is -1. Twos-complement semantics are completely reasonable here,
so we should just do the shift in unsigned.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240385 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed